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21.
P. Ricaud C. Genthon P. Durand J. -L. Attié F. Carminati G. Canut J. -F. Vanacker L. Moggio Y. Courcoux A. Pellegrini T. Rose 《Boundary-Layer Meteorology》2012,143(1):227-259
The HAMSTRAD (H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers) microwave radiometer operating at 60?GHz (oxygen line, thus temperature) and 183?GHz (water vapour line) has been permanently deployed at the Dome C station, Concordia, Antarctica [75°06??S, 123°21??E, 3,233?m above mean sea level] in January 2010 to study long-term trends in tropospheric absolute humidity and temperature. The great sensitivity of the instrument in the lowermost troposphere helped to characterize the diurnal cycle of temperature and H2O from the austral summer (January 2010) to the winter (June 2010) seasons from heights of 10 to 200?m in the planetary boundary layer (PBL). The study has characterized the vertical resolution of the HAMSTRAD measurements: 10?C20?m for temperature and 25?C50?m for H2O. A strong diurnal cycle in temperature and H2O (although noisier) has been measured in summertime at 10 m, decreasing in amplitude with height, and phase-shifted by about 4?h above 50?m with a strong H2O?Ctemperature correlation (>0.8) throughout the entire PBL. In autumn, whilst the diurnal cycle in temperature and H2O is less intense, a 12-h phase shift is observed above 30?m. In wintertime, a weak diurnal signal measured between 10 to 200?m is attributed to the methodology employed, which consists of monthly averaged data, and that combines air masses from different origins (sampling effect) and not to the imprint of the null solar irradiation. In situ sensors scanning the entire 24-h period, radiosondes launched at 2000 local solar time (LST) and European Centre for Medium-Range Weather Forecasts (ECMWF) analyses at 0200, 0800, 1400 and 2000 LST agree very well with the HAMSTRAD diurnal cycles for temperature and relatively well for absolute humidity. For temperature, HAMSTRAD tends to be consistent with all the other datasets but shows a smoother vertical profile from 10 to 100?m compared to radiosondes and in-situ data, with ECMWF profiles even smoother than HAMSTRAD profiles, and particularly obvious when moving from summer to winter. For H2O, HAMSTRAD measures a much moister atmosphere compared to all the other datasets with a much weaker diurnal cycle at 10?m. Our study has helped characterize the time variation of the PBL at Dome C with a top around 200?m in summertime decreasing to 30?m in wintertime. In summer, from 2000 to 0600 LST a stable layer is observed, followed by a well-mixed layer the remaining time, while only a nocturnal stable layer remains in winter. In autumn, a daytime convective layer shallower than the nocturnal stable layer develops. 相似文献
22.
On the Elimination of Bias Averaging-Errors in Proxy Records 总被引：2，自引：2，他引：0
Veerle Beelaerts Fjo De Ridder Nele Schmitz Maite Bauwens Frank Dehairs Johan Schoukens Rik Pintelon 《Mathematical Geosciences》2009,41(2):129-144
Knowledge of and insight into past environmental conditions can be obtained by processing and analyzing proxies. The proxies
need to be processed as precisely and accurately as possible, otherwise the conclusion of the analysis will be biased. A calibration
method which reduces bias errors in the proxy measurements due to averaging is presented. Sampling with nonzero sample sizes
causes an averaging of the true proxy signal over the volume of the sample. The method is applied on a linear synthetic record
which results in an optimal correction for frequency components ranging from the dc-frequency (DC) to one half of the sample
frequency (f
s
/2). Next, the method is tested on non-linear synthetic data where the signal is reconstructed reasonably well. Finally, the
method is applied to a real vessel density record of R.
mucronata from Makongeni, Kenya, and to a real delta deuterium record of ice core EDC from dome C, Antarctica. The method discussed
in this paper is a valuable tool for the calibration of proxy measurements; it can be applied as a correction for low resolution
measurements and expanded to other types of samples and proxies. Working with small sample sizes (high resolution) amounts
to working near the detection limit, where the signal-to-noise-ratio is low. This correction method provides an alternative
in which low resolution measurements can be upgraded to minimize the loss of information due to larger sample sizes. 相似文献
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24.
Finding the hotspots within a biodiversity hotspot: fine‐scale biological predictions within a submarine canyon using high‐resolution acoustic mapping techniques 
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下载免费PDF全文 Katleen Robert Daniel O.B. Jones Paul A. Tyler David Van Rooij Veerle A.I. Huvenne 《Marine Ecology》2015,36(4):1256-1276
Submarine canyons are complex geomorphological features that have been suggested as potential hotspots for biodiversity. However, few canyons have been mapped and studied at high resolution (tens of m). In this study, the four main branches of Whittard Canyon, Northeast Atlantic, were mapped using multibeam and sidescan sonars to examine which environmental variables were most useful in predicting regions of higher biodiversity. The acoustic maps obtained were ground truthed by 13 remotely operated vehicle (ROV) video transects at depths ranging from 650 to 4000 m. Over 100 h of video were collected, and used to identify and georeference megabenthic invertebrate species present within specific areas of the canyon. Both general additive models (GAMs) and random forest (RF) were used to build predictive maps for megafaunal abundance, species richness and biodiversity. Vertical walls had the highest diversity of organisms, particularly when colonized by cold‐water corals such as Lophelia pertusa and Solenosmilia variabilis. GAMs and RF gave different predictive maps and external assessment of predictions indicated that the most adequate technique varied based on the response variable considered. By using ensemble mapping approaches, results from more than one model were combined to identify vertical walls most likely to harbour a high biodiversity of organisms or cold‐water corals. Such vertical structures were estimated to represent less than 0.1% of the canyon's surface. The approach developed provides a cost‐effective strategy to facilitate the location of rare biological communities of conservation importance and guide further sampling efforts to help ensure that appropriate monitoring can be implemented. 相似文献
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Ann Vanclooster Nina Vanhaeren Pepijn Viaene Kristien Ooms Laure De Cock Veerle Fack 《International journal of geographical information science》2013,27(11):2284-2304
ABSTRACTPresent-day indoor navigation systems are often not well adapted to the specific needs and requirements of its users. This research aims at improving those indoor navigation systems by providing navigation support that cognitively closer to user preferences and behaviour. More specifically, the focus is on the implementation of an accurate turn calculation method in a turn minimization algorithm, aiming to lower the complexity of routes and route instructions. This new-introduced perception-based turn calculation procedure is based on a direct door-to-door walking pattern, and, in contrast to previous algorithms, independent of the underlying indoor network type. It takes into account the effects of geometry of indoor space on human movement. To evaluate its functioning, both the traditional algorithm and the proposed perception-based algorithm are applied in the fewest turns path algorithm. It is demonstrated that the proposed algorithm accurately calculates turns in alignment with people’s perception. The implementation of the calculation algorithm in the fewest turns path algorithm also allows future applications in indoor simplest path algorithms, and overall contributes to cognitively richer indoor navigation systems. 相似文献
27.
Rasha Deeb Kristien Ooms Veerle Van Eetvelde Philippe De Maeyer 《The Cartographic journal》2013,50(4):325-335
The main goal of this research is to investigate the influence of a map’s background colour on user preferences regarding labels’ typography, including their size, shape, orientation and texture. Four sets of backgrounds were tested: blank maps, grey scale, hot colours and cold colours. The foreground of these maps is populated with name labels, which are associated with point objects or areal objects. Bertin’s visual variables were applied to this set of name labels, both separately and in combination. User preferences of different typographic variations were registered and compared on the basis of different background colours using a one-way ANOVA. The results indicated that the typographic design of the map labels should not be adapted according to the map’s background colour. 相似文献
28.
Veerle Vandeginste Rudy Swennen Sarah A. Gleeson Rob M. Ellam Kirk Osadetz François Roure 《Mineralium Deposita》2007,42(8):913-935
Two Mississippi Valley-type (MVT) ore deposits, Kicking Horse and Monarch, have been studied with the aim of comparing the
ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process(es). Both
deposits are hosted by the Middle Cambrian Cathedral Formation carbonate host rocks, Kicking Horse on the north and Monarch
on the south flank of the Kicking Horse valley near Field (SE British Columbia). The ore bodies are situated at the transition
of (western) basinal to (eastern) shallow-water strata of the paleo-Pacific passive margin succession in the Cordilleran Foreland
Province of the Western Canada Sedimentary Basin. Both deposits are related spatially to normal faults. In both localities,
the ore minerals are dominated by pyrite, sphalerite, and galena. Dolomite, minor quartz, and calcite are also present in
close association with the ores. The salinity (21–30 wt% NaCl eq.) and homogenization temperatures (63–182°C) measured in
fluid inclusions in carbonate, quartz, and sphalerite lie within the typical range of MVT fluid conditions. The good stoichiometry
(50–53 mol% CaCO3), low δ18O values (−21 to −14‰ Vienna Peedee belemnite) and relatively high homogenization temperatures (>95°C) of the dolomite suggest
the dolomites were formed under burial diagenesis. The ore-forming fluids probably interacted with siliciclastic units, based
on elevated Li contents and 87Sr/86Sr ratios, which are highest in the dolomite type after the main ore stage. We propose that the ores formed from the mixing
of a downward-infiltrating, sulfur-bearing halite-dissolution fluid with an upward-migrating, metal-rich evaporated seawater
fluid, which had already undergone minor mixing with a dilute fluid. 相似文献
29.
River channel response to short-term human-induced change in landscape connectivity in Andean ecosystems 总被引：4，自引：2，他引：4
Veerle Vanacker Armando Molina Gerard Govers Jean Poesen Gerd Dercon Seppe Deckers 《Geomorphology》2005,72(1-4):340-353
The drainage basin of the Deleg River (88 km2), located in the southern Ecuadorian Andes, was studied to assess the geomorphic and hydrologic response of a fluvial system to human-induced environmental change in its contributing area. Historical data on land use, channel morphology and sedimentology were collected, based on a spatial analysis of aerial photographs (1963–1995) and a field survey (2002). Analysis of channel cross-sectional profiles and sedimentological data revealed a major change in morphology and sedimentology of the Deleg River during the past four decades: (i) the active river channel narrowed by over 45%, (ii) the riverbed incised on average by over 1.0 m and (iii) the median grain size of the bed surface decreased from 13.2 cm to 4.7 cm. The spatial pattern of land cover within the Deleg catchment also changed considerably: highly degraded agricultural land in the low-lying areas was abandoned and partially afforested for timber and wood production, whereas secondary upland forest was increasingly cleared for expansion of cropland and pastures. Notwithstanding large changes in the spatial organization of land use within the catchment, the overall land use did not change significantly during the past four decades. This suggests that the response of the Deleg River to land-use change not only depends on the overall land-use change, but also on the spatial pattern of land-use/cover change within the catchment. Although forestation and regeneration of bare gully slopes and floors throughout the catchment only represented a minor part of the total land-use change, these land-use/cover changes had a major impact on the hydrological and sediment connectivity in the landscape. 相似文献
30.